In a large pot, combine 8 cups water, 1 cup EACH lentils and barley (rinsed). Bring to a boil. Cover tightly, reduce heat and simmer until they are tender, about 15-20 minutes (avoid overcooked/split lentils). Drain and rinse in cold water to cool completely (keeps 5 days in fridge). Set aside. You can also use canned lentils and leftover barley.